Thread: Timber fame and floor inside detached Garage

i am wanting to build a room within a room in a double garage of brick that already has a brick dividing wall, basically 1/3 for tools, 2/3 for car.

The cement has some dampness, telling me no plastic under concrete. So, damp and moisture problems come to mind.

The internal build will consist of the following:

H3 (Moisture and Mites) timber wall frame 2 inch off external brick wall, and ceiling frame (ceiling frame will attach from current timber beam to beam of space of 1.7m)

12mm Ply walls and ceiling with insulation (Bradford soundproof or Gold batts)

But the floor? Nearly thinking of being done with it and get Spantec. What else can i do here keeping mind some dampness (not pools of water)?

eg: Should I use Crommelin Dampstop and then Crommelin Waterproofing-Exterior-Grade-Brushable-Waterproofer, and/or just lay plastic on top of concrete and build timber frame floor over that. For the floor frame, will 75x50 Hardwood be too effected and bow if i don't fix to the concrete and depend on the weight of tongue in groove sheets (over vapour barrier). Can I just use H3 timber for the floor using this method? Or go bigger H3 145x45, but this is losing headspace.

When you put plastic over the concrete, how will the damp dry out, or am i not caring about that anymore?

Any advice is much appreciated!